WordNet (r) 3.0 (2006):

fall from grace
    v 1: revert back to bad behavior after a period of good
         behavior; "The children fell from grace when they asked for
         several helpings of dessert"

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "fall from grace":
   apostasy, atheism, backslide, backsliding, desertion, fall,
   fall again into, fall back, fall of Adam, fall of man,
   have a relapse, impiety, impiousness, irreligion, irreverence,
   lapse, lapse back, lapse from grace, recidivate, recidivation,
   recidivism, recreancy, recur to, regress, relapse, return to,
   revert, revert to, sin of Adam, sink back, slide back, slip back,
   undutifulness, yield again to